Microsoft has limited the Office 2016 for Windows preview to customers with subscriptions to the enterprise-grade plans ProPlus, E3 and E4.

The restriction took some users by surprise.

"The software appears to be looking for an Office 365 Professional Plus subscription instead of the Business/Business Premium/E plan subscriptions. The Connect page says otherwise," wrote someone identified as Rekab in a message posted to Microsoft's support forum on Monday after downloading the preview.

"I can confirm that after upgrading our Office 365 account to the E3 level I am able to successfully activate the Office 2016 Preview with my corporate account," replied Jrausch later that day. "Looks like the problem is that you need one of the Enterprise level subscriptions to use the Preview. That was not clear at all from the information that accompanied the announcement from Microsoft."

Messages on other threads confirmed that the Office 2016 preview was not available to all Office 365 business plan subscribers. "Office 365 ProPlus, E3, and E4 are the only subscription types that I've seen work," said Jaxidian today.

The reason users complained was that on Monday, when Microsoft announced the Office 2016 Preview for Business, it said that a business-grade Office 365 subscription was required. That implied customers with, say, Office 365 Business Premium, or its forerunner, Office 365 Small Business Premium, would be able to test the new suite.

ProPlus is available as a separate subscription -- for $12 per user per month -- but it is also bundled with the Office 365 Enterprise E3 and E4 plans, which run $20 and $22 per user per month, respectively.

Microsoft will expand the preview to a wider audience -- it typically limits betas before opening them to all comers -- but has not said when it will do so.

People interested in testing the Office 2016 preview must register on Microsoft Connect.

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